linux-kernel - RE: [PATCH 1/2] armv8: aarch32: Execute 32-bit Linux for LayerScape platforms

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Date:   Fri, 23 Sep 2016 13:13:17 +0000
From:   Stuart Yoder <stuart.yoder@....com>
To:     Robin Murphy <robin.murphy@....com>,
        Alison Wang <b18965@...escale.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        Fabio Estevam Estevam <fabio.estevam@....com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Scott Wood <scott.wood@....com>, Leo Li <leoyang.li@....com>
CC:     Jason Jin <jason.jin@....com>
Subject: RE: [PATCH 1/2] armv8: aarch32: Execute 32-bit Linux for LayerScape
 platforms



> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@....com]
> Sent: Friday, September 23, 2016 7:17 AM
> To: Alison Wang <b18965@...escale.com>; shawnguo@...nel.org; kernel@...gutronix.de; Fabio Estevam
> Estevam <fabio.estevam@....com>; linux@...linux.org.uk; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; Scott Wood <scott.wood@....com>; Stuart Yoder <stuart.yoder@....com>; Leo Li
> <leoyang.li@....com>
> Cc: Jason Jin <jason.jin@....com>
> Subject: Re: [PATCH 1/2] armv8: aarch32: Execute 32-bit Linux for LayerScape platforms
> 
> Hi Alison,
> 
> On 23/09/16 03:19, Alison Wang wrote:
> > The ARMv8 architecture supports:
> > 1. 64-bit execution state, AArch64.
> > 2. 32-bit execution state, AArch32, that is compatible with previous
> > versions of the ARM architecture.
> >
> > LayerScape platforms are compliant with ARMv8 architecture. This patch
> > is to support running 32-bit Linux kernel for LayerScape platforms.
> >
> > Verified on LayerScape LS1043ARDB, LS1012ARDB, LS1046ARDB boards.
> >
> > Signed-off-by: Ebony Zhu <ebony.zhu@....com>
> > Signed-off-by: Alison Wang <alison.wang@....com>
> > ---
> >  arch/arm/Kconfig                    |  9 +++++++++
> >  arch/arm/mach-imx/Kconfig           | 14 ++++++++++++++
> >  arch/arm/mach-imx/Makefile          |  4 +++-
> >  arch/arm/mach-imx/mach-layerscape.c | 23 +++++++++++++++++++++++
> >  4 files changed, 49 insertions(+), 1 deletion(-)
> >  create mode 100644 arch/arm/mach-imx/mach-layerscape.c
> >
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index f0c8068..e8d470e 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -294,6 +294,15 @@ config PGTABLE_LEVELS
> >  	default 3 if ARM_LPAE
> >  	default 2
> >
> > +config ARCH_AARCH32_ES_SUPPORT
> > +	def_bool n
> > +	help
> > +	 The ARMv8 architecture supports 64-bit execution state, AArch64
> > +	 and 32-bit execution state, AArch32, that is compatible with
> > +	 previous versions of the ARM architecture.
> > +
> > +	 Enable AArch32 execution state support for ARMv8 architecture.
> 
> What's this supposed to do, exactly? I've been running 32-bit kernels on
> my Juno with very little issue (beyond a couple of DT tweaks, and some
> firmware hacks with a corresponding bit of A64 assembly tacked on the
> front of the zImage to switch into AArch32 state).

Which arch/arm/mach-* platform are you using for Juno?

Thanks,
Stuart